Progress in the Understanding and Manipulation of Desiccation-Sensitive (Recalcitrant) Seeds

Abstract

Seeds of many species behave in a ‘non-orthodox’ manner and have been variously categorized as sub-orthodox, intermediate or recalcitrant. Those of some species have been recorded as showing anomalous behaviour in their being placed in more than one of these categories. Individual seed species may, in fact, be assigned to some point on a behavioural continuum subtended by the extremes of orthodoxy and recalcitrance. The nature of seed recalcitrance is discussed in terms of two components, desiccation sensitivity and post-harvest behaviour. Both components differ among species, and seeds of any one species may show variability within or between seasons. Developmental stage and the tissue water status influence both these components and show considerable variation among species and within individual species inter- and intra-seasonally. This variability may, to some extent, contribute to supposedly anomalous behaviour. Storage lifespan is also affected by the seed-associated mycoflora. Practical problems associated with short-term storage of hydrated recalcitrant seeds, and the possibility of cryopreservation for long-term storage are also important issues.